Oftentimes it is useful for anyone who lives in a house, apartment, tent, or other environment or who works in an office, school, warehouse, factory, farm, zoo, underground mine or other enclosed space to find misplaced items. One might want to find books, keys, tools, papers, various equipment, magazines or anything else that can be lost in a building or crowded area.
As will be apparent, tools can fall from a workbench. Books can be mislaid on a couch behind pillows or in another room. Items such as remote clickers, eyeglasses, and even such items as small as a screw or bolt can oftentimes get lost and a great deal of time is spent trying to locate these items.
In the past, EPC-standard RFID tags have been used to identify items, with the RFID tags encoded with appropriate identification information such as a barcode. Additionally, golf balls can be found by a so-called Radar Golf Ball Finder, with the technology used described in United States Patent Application Publication Number U.S. 2006/0128503. In this Patent Publication a golf ball locator receives RF signals back from an RF circuit within the golf ball. The range to the golf ball is determined by the received signal strength using a received signal strength indicator, or RSSI, with a threshold being set to indicate golf ball detection. In one embodiment of the golf ball locator, the carrier from the locator is modulated to provide a spread spectrum binary phase shift keyed, BPSK, modulated signal, where the modulation includes a pseudo-random binary sequence, also known as a pseudo noise or PN code. Transmitted pulses are used to locate the golf ball which has an RF circuit that returns a harmonic of the transmitted signal back to the locator.
Additionally, RFID tags have been utilized to locate animals in which an RFID tag is attached to the animal.
One problem with all of the above RFID applications is that they operate out in the open. There are no multi-path or standing wave problems in which signals bounce off metal in the urban environment and building structures which makes indoor reading of RFID tags difficult. These applications are quite different from RFID readers which are adjacent tagged articles and which operate at low power.
The problem with EPC-standard RFID tags is that they are intentionally limited in range due to limits on the transmit power established by the Federal Communications Commission. What typically happens with an RFID tag is that energy from a source is used to power the tag, with the tag then re-radiating its code back to the source, whereby the tag is identified. The Federal Communications Commission intentionally limits the amount of power that can be utilized to power these tags so that the tag must be relatively close to the interrogating head in order for the RFID tag to work.
With respect to radar golf, the radar golf system discussed above does not distinguish which golf ball is detected and is range-limited to approximately 100 feet. As to animal tags, the tags have batteries and are difficult to reconfigure.